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The Biosphere
Chapter 3
What is Ecology?
Ecology
•The study of the interactions among
organisms and between organisms
their environment.
Biosphere
All parts of the Earth
where life can exist
(land, water and
air).
Biotic vs. Abiotic
Biotic: the living
factors in an
ecosystem
Abiotic: the
nonliving factors
in an ecosystem
Levels of Organization
 Ecosystem: interactions
among the community and
abiotic factors
 Community: group of
interacting populations
 Population: group of one
species living in the same place
at the same time
Energy, Producers, and
Consumers
Autotrophs
• An organism that
can make its own
food.
• Use photosynthesis
or chemosynthesis.
• Also called
producers.
Heterotrophs
• An organism that
has to get its food
from others.
• Also called
consumers.
Types of Heterotrophs
Herbivores: eat only plants
Carnivores: eat only meat
Omnivores: eat both plants and meat
Detritovores: break down dead
material; decomposers
Scavengers: eat dead animals
Energy Flow in Ecosystems
Feeding Relationships
• Food chains: less complex
• Food webs: show all eating
relationships in an ecosystem. BETTER!
Trophic Levels
• Each step in a
food chain.
• As you move up
trophic levels,
90% of the
energy is lost.
Ecological Pyramids
• Energy Pyramid
(kCal)
Cycles of Matter
The Water Cycle
Nutrient
Chemicals an organism needs to sustain
life.
Carbon
Nitrogen
Phosphorous
Limiting nutrient: the nutrient whose
supply limits productivity of producers
Carbon Cycle
Nitrogen Cycle
Phosphorous Cycle
Ecosystems &
Communities
Chapter 4
Niches & Community
Interactions
Niche
• Everything an organism does to survive.
• All physical and biological conditions.
• What it eats, where it lives (habitat),
how it avoids predators, etc.
Competition
Occurs when two organisms want the
same resource at the same time.
Competitive Exclusion Principle: No
two species can occupy the same niche
at the same time.
Predation
• An interaction where one organism
captures and feeds on another
organism.
• Predator: the “killer”
• Prey: the “killed”
Keystone Species
A species that exerts strong control on
the structure of a community so that
changes to its population causes
dramatic changes
Ex: sea otters
Symbiosis
• Any relationship in which two species live closely
together.
• Mutualism: both species benefit
• Ex: bees and flowers
• Commensalism: one species benefits while the
other is not affected
• Ex: barnacles on a whale
• Parasitism: one species benefits, while the other is
harmed
• Ex: tapeworms- YUK!
Examples of Symbiosis
Succession
Ecological Succession
• The series of predictable changes that occur
in an ecosystem over time.
• Primary Succession: occurs where there is no soil
• 1st: lichens; 2nd: mosses; 3rd tree seedlings appear
• Ex: after a volcano erupts
• Secondary Succession: occurs where there is soil
• Ex: after a forest fire
Climate
Weather vs. Climate
•Weather: the day to day condition of
the Earth at a particular time and place
•Climate: the average, year-to-year
conditions of temperature and
precipitation
Effect of Latitude on Climate
• The tilt of the Earth
creates climate
zones based on
latitude:
• Polar
• Temperate
• Tropical
Heat Transport in the
Biosphere
• Unequal heating of
the Earth drives
winds and ocean
currents.
• Air and water near
the equator heats
and rises.
Ozone Layer
• Layer of the Earth’s atmosphere (13-20
km above Earth) containing ozone (O3).
• Absorbs 93-99% of UV light.
The Greenhouse Effect
• Natural situation where
gases trap the sun’s heat
energy in the atmosphere.
• Maintains our climate. (Earth
would be 30 ºC cooler
without it.)
Humans in the Biosphere
Carrying Capacity
The maximum number of individuals of
a particular species that a particular
environment can support.
Resources
Renewable Resource: can be
replaced by a healthy ecosystem
Ex: trees, wind
Nonrenewable Resource: can’t be
replenished by natural processes in a
reasonable amount of time
Ex: fossil fuels
Biological Magnification
Increasing concentration of a harmful
substance in organisms at higher
trophic levels in a food chain
Biodiversity
All of the organisms in the biosphere
Ecological hot spot: a place where
significant numbers of species and habitats
are in immediate danger of extinction
Conservation
“wise use”
 studying the loss of biodiversity & ways
it can be prevented
Ecological footprint
The total area of functioning land and
water ecosystems needed to provide
resources and absorb the wastes of an
individual or population.
Used to calculate the biosphere’s carrying
capacity for humans.